U.S. Secretary of Defense Ash Carter (C) is greeted by Senior Military Assistant U.S. Army Major General Ron Lewis (L) as they arrive to travel to Afghanistan from Joint Base Andrews, Maryland February 20, 2015.

New U.S. Defense Secretary Ash Carter arrived in Afghanistan on Saturday on his first trip since taking over the job this week, saying he wanted to talk to Afghan and American officials to ensure a "lasting" success as U.S. troops withdraw.

Carter, who was sworn in on Tuesday, has suggested he would be open to slowing U.S. withdrawal plans, if necessary. But he did not signal whether he was leaning in that direction in comments to reporters shortly before landing in Kabul.

"We’re looking for success in Afghanistan that is lasting, and the lasting accomplishment of our mission here," Carter said in his first news conference since taking the job.

"How to do that, what the best way to do that is, is precisely what I’m here to assess."

President Barack Obama's plans call for cutting U.S. troops from about 10,000 now to 5,500 by the end of this year and drawing down to a U.S. embassy presence in Kabul at the end of 2016.

The drawdown strategy has also drawn sharp criticism from Republicans in Congress, who say that the hard-fought gains made against the Taliban could be lost in much the same way that sectarian violence returned to Iraq after the U.S. withdrawal.

Obama is weighing a request from Afghan President Ashraf Ghani to slow the withdrawal plans, and the top U.S. commander in Afghanistan has also publicly signaled that he is seeking greater flexibility in the months ahead.

Carter, a former Pentagon No. 2, said Obama wanted him to make his own assessment and did not rule out recommending "adjustments" if necessary.

Carter said he looked forward to an update from Ghani and added the two would discuss Afghan government-led peace efforts with Taliban militants.

Senior Pakistani army, Afghan and diplomatic officials said on Thursday the Afghan Taliban had signaled they were willing to open peace talks with Kabul.

Asked about peace prospects, Carter said: "I'll have a better chance to assess that after I've heard from him, because he's really in the driver's seat of that process.

"Obviously we're supportive of it but it's Afghan-led," he said.

Carter’s unannounced visit to Afghanistan came after the bloodiest year in Afghanistan since the war against Taliban militants began in 2001.

Afghanistan's national army and police suffered record losses last year, with nearly 5,000 killed, a pace that U.S. military officials caution is unsustainable.

A total of 3,699 Afghan civilians were killed, according to U.N. data, as fighting intensified in tandem with the sharp drawdown of U.S. and allied foreign troops who formally ended their combat role in December.

The emergence of a small number of militants in Afghanistan aligning themselves with the Islamic State, which swept into northern Iraq last summer, has underscored anxieties about the dangers as foreign forces withdraw.

Carter suggested any threat from the Islamic State in Afghanistan was minimal.

"I’ve see the reports of people essentially rebranding themselves as ISIL here in Afghanistan, as has occurred in other places," Carter said, using an acronym for the militant group.

"The reports I’ve seen still have them in small numbers, and aspirational."